By any reasonable non-political definition, Eurasia is a single continent. Its area is 54,759,000 km², which is over one-third the earth’s total land area.
The politics of history have created, however, the “continents” of Europe, with an area of 10,180,000 km² (18.59% of Eurasia), and Asia, with an area of 44,579,000 km² (81.41% of Eurasia). These figures for Asia’s land area include that of the “subcontinent,” India, which has an area of 4,400,000 km². (Note: the subcontinent of India is a geographical term, and does not match the borders of the nation of India perfectly. The major reason for this is that India the subcontinent includes the nations of Pakistan and Bangladesh, in addition to the politically-defined nation of India.) The subcontinent’s area is 8.04 % that of Eurasia, and 9.87% that of Asia.
Europe is a large peninsula, a part of Eurasia with a sizeable portion of its area. So is the Indian subcontinent. So, for that matter, are the Southern portions of both South America and Africa, yet no one calls them separate continents, nor even subcontinents.
Giving India a special designation of “subcontinent” makes no sense, nor does the designation of Europe as a separate continent. Both are simply parts of Eurasia.